Supporting structure



April 5, 1966 o. A. DRAKE ETAL SUPPORTING STRUCTURE Filed Oct. 18, 1963Pr/or Ari fiea Y O M M T N u R EE 0 WAT W mm A a Y4 B United StatesPatent a corporation of Delaware Filed Oct. 18, 1963, Ser. No. 317,295 3Claims. (Cl. 313-270) This invention relates to electrode supportingmeans in electron discharge devices and more particularly to means forinsulatively spacing and supporting the components of a cathode assemblywithin a companion electrode structure for use in a cathode ray tube.

It has been conventional practice in the manufacture of cathode raytubes to employ cathodes utilizing heat responsive electron emissivematerial as the source of beam energy. In devices of this nature thecathode usually comprises a cylindrical metal sleeve capped on one endwith electron emissive material. There is disposed within the cathodecylinder a heater or resistance filament. A ceramic insulating disc,having an axial aperture therein, is normally used to position andsupport the cathode within a cup-shaped grid electrode having anapertured bottom.

It is operationally essential to have the cathode positioned in a mannerthat the emissive material thereon is properly oriented and spacedrelative to the grid electrode aperture. It is also highly importantthat the cathode be mounted in its supporting structure to be spacedfrom the grid by an adequate amount of insulation in the form ofinsulative material thickness or area or both. Metallic vaporizationemanating as sublimation from the heated cathode deposits on thesurrounding areas, including the insulating area, and thusly promotesthe formation of electrical leakage paths thereacross. Therefore, it isparamount that the cathode structure be properly disposed in its supportwafer relative to the adjacent grid electrode to assure an adequateelectrical insulative area or barrier therebetween.

In one supporting method, the cathode cylinder is disposed in the discaperture and fixed therein by means of swages or ferrules which contactthe ceramic disc completely around the cathode cylinder. The disc beingfixedly oriented within a circular metal retainer which is, in turn,positioned within the grid structure and afiixed thereto. This methodaffords considerable insulation between the cathode structure and thegrid but the swaging has a disadvantage in that it is ditficult toachieve necessary and consistent tightness of the cathode in theinsulator without fracturing the ceramic insulator. This factor oftightness assumes greater importance in color cathode ray tubeapplications where it is imperative to have the cathode rigidly anchoredin the insulator. Any looseness of the cathode varies the criticaloperational cathode to grid spacing thereby generating deterimentalspurious signals that are visibly manifest during tube operation.

By another supporting method conventionally utilized in color cathoderay tubes, the cathode cylinder is spacedly telescoped within a largercylindrical cathode eyelet with the bottom end of the cathode beingsuitably joined to the bottom end of the eyelet. The cathode eyeletcylinder is then oriented within the axial aperture and mounted thereinby peripheral seating means integral to the top or terminal end of theeyelet.

A retainer for positioning the disc within the adjacent grid electrode,having a circumferentially oriented seating surface to accommodate thedisc, is likewise joined to the surface of the disc adjacent the eyeletseat but spaced therefrom.

The eyelet and the retainer are insulated from one an- 3,244,927Patented Apr. 5, 1966 ice other by the width of the circular interveningarea of disc surface separating the adjacent edge of each. To provideadequate rigidity of the cathode eyelet with the disc, and the discwithin the retainer, certain limitations of hearing or seating surfacewidths must be maintained along with adequate insulative spacingtherebetween. In

addition, in certain color tube applications it is desirous tominiaturize or further decrease the diametrical size of the disc. As thedisc size is decreased, surface grooves are sometimes used to increasethe surface or insulation area and produce insulative shadowing betweenthe edges of the eyelet and the retainer, but obviously there is a theaforementioned disadvantages by providing an im proved cathode structuresupporting member having superior insulative qualities.

' A further object is to improve the insulation barrier between thecathode structure and the adjacent electrode.

Another object of the invention is to provide a miniaturecathode-support structure adapted to rigid cathode mounting and havinginsulative spacings in leakage prone areas.

The foregoing objects are achieved in one aspect of the invention by theprovision of a disc-like insulating support adapted to accommodate acathode-containing eyelet and a support retainer each of which isseparately and spacedly afiixed thereto on different surfaces or surfacelevels thereof.

For a better understanding of the present invention, together with otherand further objects, advantages and capabilities thereof, reference ismade to the following disclosure and appended claims in connection withthe accompanying drawings in which:

FIGURE 1 is a sectional view illustrating a cathodegrid assemblycomprising a heater, a cathode, a cathode eyelet, and an insulatingsupport adapted for mounting within a grid structure as utilized in theprior art; and

FIGURES 2 through 4 are cross-sectional views showing variousmodifications of the cathode support structures embodying the invention.

In referring to FIGURE 1 there is shown a representation of theaforementioned prior art wherein a ceramic supporting disc 20 having acathode structure 21 rigidly afiixed therein is attachced to a supportretainer 37 which is positionally mounted within an apertured gridelectrode 41. An insulated heater 24 suitably disposed within cathode 23functionally completes the assembly. In greater detail, cylindricalcathode 23 having electron emissive material 25 disposed on the cappedend 26 thereof is spacedly telescoped within the cylindrical cathodeeyelet 27 and joined thereto at one end by a welding jointure 28. Theeyelet is adapted for insertion within the axial aperture 39 of ceramicdisc 20. Integral to the open terminal end of the eyelet 27 is anoutstanding seating ledge 29 formed to facilitate a braze jointure withdisc 20 on the metallized surface area 32 surrounding the aperture 30.

Supporting disc 20 has a second circular metallized area 33 onsubstantially the peripheral area of the aforementioned disc surface.

A metal support retainer 37, dimensioned for sliding placement withingrid electrode 41 and adapted to receive disc 20 is formed with asubstantially instanding seating ledge 38 adapted for bonding to theperipheral metallized area 33 on ceramic disc 20. Thus a rigidcathode-grid assembly 45 is constructed wherein electrical insulationbetween the cathode structure 21 and the grid electrode 41 is effectedby the ceramic surface spacing 35. It is clearly evident that as thediametrical size of the cathodegrid assembly 45 decreases, as is thecase in the development of color cathode ray tube art, a condition isreached wherein inadequate insulative spacing 35 exists between theedges of eyelet seating means 29 and retainer ledge 38. Thus, practiceof the aforedescribed prior art limits successful miniaturization of thecathode-grid assembly 45.

Now advertising to the structures of the invention as exemplified inFIGURES 2 through 4, it is evident that much greater miniaturization ofthe cathode-grid assembly is feasible. For clarity and simplicity onlythe cross-sectional manifestations of the ceramic support, the cathodeeyelet and the support retainer are illustrated.

In FIGURE 2 there is shown a substantially planar ceramic supportingdisc 50 having a first surface 51 and A cathode eyelet 50 of nickel orstainless steel material and similar to the previously described eyelet27, is aligned within the axial aperture 54 so as to be removed, frominternal wall 53 providing a space 56 therebetween. The terminallyformed outstanding seating edge 63 on the eyelet is conventionallywelded or brazed to effect a circumferential bond 67 with the circularmetallized area 55 on the first surface .51 of theceramic supportingdisc 50 The term circumferential bonding, as used in this specification,may be defined as a continuous bond or a' plurality of spaced spot-bondseffective equi-circumferential support.

A11 insulator retainer 71 formed of a metal such as stainless steel ornickel is utilized for supporting and positioning the ceramic insulatingdisc 50. This metal retainer terminally formed to have aninstandingseating ledge 73 which mates with the peripheral metallizedarea. 57 on the second surface 52 of ceramic 50 and is likewisecircumferentially bonded thereto by welding or brazing.

The insulative advantages realized in this type of ceramic support areclearly evident as the construction affords maximum insulation areabetween the cathode eyelet and the grid.

Another embodiment is shown in FIGURE 3 wherein a disc-like ceramicsupport insulator 80, having an axial aperture 81, therein has a steppedfirst surface 82 comprising at least a rasied first circular level 83and a lower circular second level 86. The second surface 91 of theceramic is substantially planar. The first level 83 has a circularmetallized area 84 disposed adjacent the aperture 81 and the second orlower level 8.6 has a similar but circularly larger metallized area 87disposed adjacent the periphery of the ceramic disc 80.

The cathode eyelet 60 is spacedly positioned within the aperture asdescribed in the previous embodiment and the seating edge 63 suitablybonded to metallized area 84.

A metal insulator retainer 95 is terminally formed to have an instandingseating ledge 99 and has an internal dimension at least equal to thediameter of the insulator 80 to permit placement of the insulatortherein; ledge. 99 being circumferentially bonded to metallized area 87on the second level 85.

In this embodiment, the stepped construction of the first surface 82affords an insulative area 89 between the peripheral boundary of theraised first level 83 and this inner boundary of the lower second level86. This in- 4i sulative area 89 is oriented so as to be shadowed fromsublimation by the first raised level 83.

In an alternate embodiment as illustrated in FIGURE 4, there is shown adisc-like support insulator 102, having an axial aperture 104 therein, aplanar first surface 106 and a stepped second surface 108. The firstsurface has a circular metallized area 110 adjacent the aperture 104.The eyelet 60, as aforedescribed, is positioned within the aperture andthe seating edge 63 bonded to metallized area 110.

The second surface 108 has thereon a first circular level 112 proximalto aperture 104 and a recessed second level 114 distal to the apertureoccupying the peripheral area of the second surface. This second level114 has metallizing 115 disposed thereon and is circumferentially bondedby welding or brazing to ledge 73, of retainer 71.

The stepped construction of the second surface 108 of the supportinsulator 102 shown in FIGURE 4 affords not only the insulative area ofthe first level 112 but also that of insulative area 117 which byorientation is shadowed by the first level. Thus, the recessing of thesecond level 114 augments the insulative properties of the secondsurface.

It is evident from the several embodiments shown that the inventionprovides a miniature ceramic cathode supporting structure that has bothsuperior insulative properties and rugged construction.

While there have been shown and described what are at present consideredthe preferred embodiments of the invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention as defined by the appendedclaims.

What is claimed is:

1. In a thermionic electron discharge device, integral means forsupporting the cathode within a miniature cylindrical grid electrodehaving a given internal diameter comprising:

a circular support insulator having an upper first surface and anoppositely disposed lower second surface with said insulator thicknessdefining the distance therebetween, each of said surfaces having atleast one planar level with at least a portion of said insulatorthickness constituting the distance there- 'between, said insulatorhaving an internal wall defining an axial aperture therethrough, saidinsulator being of a diameter smaller than the internal diameter of saidelectrode;

a substantially cylindrical eyelet encompassing said cathode andconnected therewith, said eyelet being disposed within said axialaperture and spaced from the internal wall of said insulator, saideyelet having a terminally formed outstanding peripheral seat secured tosaid first surface of said insulator to effect spalced alignment of saideyelet within said aperture; an

an insulator retainer internally dimensioned to at least equal thediameter of said support insulator and adapted to slide within said gridelectrode for affixation thereto, said retainer having a terminallyformed instanding ledge secured to said insulator on a planar levelbelow the one accommodating said eyelet.

2. In a thermionic electron discharge device, integral means forsupporting a cathode within a miniature cylindrical grid electrodehaving a given internal diameter comprising:

a substantially disc-like support insulator formed of first and secondoppositely disposed surfaces having said insulator thicknessconstituting the vertical distance therebetween, said insulator havingan internal wall defining an axial aperture therethrough, said firstsurface having at least a raised first circular level proximal to saidaperture and a lower circular second level distal thereto with a portionof said insulator thickness defining a substantially vertical insulativearea therebetween to efiect at least a partial shadowing of said secondlevel by said first level to inhibit sublimation leakage thereacross,said first level having a circular area adjacent said aperture surface.

sulator thickness defining a substantially vertical insulative areatherebetween to effect at least a partial shadowing of said second levelby said first level to inhibit sublimation thereacross, said first leveland said second level being substantially planar and 5 having a circulararea adjacent said aperture and having a circular area adjacent theperiphery theresaid second level having a circular area adjacent the ofsaid support insulator being of a diameter smaller peripheral boundarythereof, said support insulator than the internal diameter of saidelectrode; being of a diameter smaller than the internaldiamsubstantially cylindrical eyelet encompassing said eter of saidelectrode;

cathode and connected therewith, said eyelet being 10 substantiallycylindrical eyelet encompassing said disposed Within said axial apertureand spaced from cathode and connected at one end therewith being saidinternal wall thereof, said eyelet having a termidisposed within saidaxial aperture and spaced from nally formed outstanding seating ledgeafiixed to said internal wall thereof, said eyelet having a termionlysaid first surface of said support insulator on nally formed outstandingseating ledge circumferensaid first level thereof on the area proximalto said tially secured to only said first surface of said supaperture toeffect spaced alignment of said eyelet port insulator on said firstlevel thereof on the area within said aperture; and proximal to saidaperture to effect spaced alignment an insulator retainer externallydimensioned to slide of said eyelet within said aperture; and

within said electrode for aflixation thereto, said rean insulatorretainer externally dimensioned to slide tainer having an internaldimension at least equal Within said electrode for affixation thereto,said reto the diameter of said insulator to permit insulator tainerhaving an internal dimension at least equal placement therein, saidretainer being terminally to the diameter of said insulator to permitinsulator formed with an instanding seating ledge secured to placementtherein, said retainer being terminally said support insulator on theperipheral metallized formed with an instanding seating ledgecircumferenarea on only the lower second level of said first tiallysecured to said support insulator on the peripheral area on only thelower second level of said first surface.

3. In a cathode ray tube, integral means for supporting a cathode withina miniature cylindrical first grid electrode having a given internaldiameter comprising:

a substantially disc-like ceramic support insulator formed of first andsecond oppositely disposed sur- References Cited by the Examiner UNITEDSTATES PATENTS faces having said insulator thickness constituting the gg 2 5% vertical distance therebetween, said insulator having ame2,907,963 1/1961 Ballard et a1. 313-82 X an mternal wall defining anaxial aperture there- 2978 606 4/1961 K hl 313 270 X through, said firstsurface having a stepped topoga 3,026,438 3/1962 Warne 313-82 X raphydefining at least a raised first circular level 3 128 407 4/1964 M n 313268 having an inner boundary proximal to said aperture a Son and aperipheral boundary removed therefrom and a lower circular second levelhaving an inner bound- FOREIGN T P ary distal to said aperture and aperipheral bound- 4 772,597 4/ 1957 Great Bntamary removed therefrom,said second level inner boundary having a circumference at least equalto that of the peripheral boundary of said first level being separatedtherefrom by a portion of said in- JOHN W. HUCKERT, Primary Examiner.

DAVID J. GALVIN, Examiner.

A. 1. JAMES, Assistant Examiner.

2. IN A THERMIONIC ELECTRON DISCHARGE DEVICE, INTEGRAL MEANS FORSUPPORTING A CATHODE WITHIN A MINIATURE CYLINDRICAL GRID ELECTRODEHAVING A GIVEN INTERNAL DIAMETER COMPRISING: A SUBSTANTIALLY DISC-LIKESUPPORT INSULATOR FORMED OF FIRST AND SECOND OPPOSITELY DISPOSEDSURFACES HAVING SAID INSULATOR THICKNESS CONSTITUTING THE VERTICALDISTANCE THEREBETWEEN, SAID INSULATOR HAVING AN INTERNAL WALL DEFININGAN AXIAL APERTURE THERETHROUGH, SAID FIRST SURFACE HAVING AT LEAST ARAISED FIRST CIRCULAR LEVEL PROXIMAL TO SAID APERTURE AND A LOWERCIRCULAR SECOND LEVEL DISTAL THERETO WITH A PORTION OF SAID INSULATORTHICKNESS DEFINING A SUBSTANTIALLY VERTICAL INSULATIVE AREA THEREBETWEENTO EFFECT AT LEAST A PARTIAL SHADOWING OF SAID SECOND LEVEL BY SAIDFIRST LEVEL TO INHIBIT SUBLIMATION LEAKAGE THEREACROSS, SAID FIRST LEVELHAVING A CIRCULAR AREA ADJACENT SAID APERTURE AND SAID SECOND LEVELBEING SUBSTANTIALLY PLANAR AND HAVING A CIRCULAR AREA ADJACENT THEPERIPHERY THEREOF SAID SUPPORT INSULATOR BEING OF A DIAMETER SMALLERTHAN THE INTERNAL DIAMETER OF SAID ELECTRODE; A SUBSTANTIALLYCYLINDRICAL EYELET ENCOMPASSING SAID CATHODE AND CONNECTED THEREWITH,SAID EYELET BEING DISPOSED WITHIN SAID AXIAL APERTURE AND SPACED FROMSAID INTERNAL WALL THEREOF, SAID EYELET HAVING A TERMINALLY FORMEDOUTSTANDING SEATING LEDGE AFFIXED TO ONLY SAID FIRST SURFACE OF SAIDSUPPORT INSULATOR ON SAID FIRST LEVEL THEREOF ON THE AREA PROXIMAL TOSAID APERTURE TO EFFECT SPACED ALIGNMENT OF SAID EYELET WITHIN SAIDAPERTURE; AND AN INSULATOR RETAINER EXTERNALLY DIMENSIONED TO SLIDEWITHIN SAID ELECTRODE FOR AFFIXATION THERETO, SAID RETAINER HAVING ANINTERNAL DIMENSION AT LEAST EQUAL TO THE DIAMETER OF SAID INSULATOR TOPERMIT INSULATOR PLACEMENT THEREIN, SAID RETAINER BEING TERMINALLYFORMED WITH AN INSTANDING SEATING LEDGE SECURED TO SAID SUPPORTINSULATOR ON THE PHERIPHERAL METALLIZED AREA ON ONLY THE LOWER SECONDLEVEL OF SAID FIRST SURFACE.